With the explosion of the Internet and other communications needs, there is an on-going need for faster communications networks. Long haul communications are often accomplished over an optical network. An optical communication system includes a transmitter that encodes a message into an optical signal, a channel that carries the signal to its destination, and a receiver that reproduces the message from the received optical signal.
In fiber-optic communications, wavelength-division multiplexing (WDM) is a technology that combines (multiplexes) a number of optical carrier signals onto a single optical fiber by using different wavelengths of laser light. Since its first deployment in the middle of 1990s, dense wavelength division multiplexing (DWDM) has become a dominant technology for long haul and regional backbone transport networks, and is gradually making its way to metro area networks.
The combination of the different light beams can be implemented using an optical multiplexer. An optical multiplexer merges a number of optical signals that are each at a different optical wavelength into optical alignment as a single multiplexed signal. For example, optical signals produced at different optical wavelengths by a corresponding number of distinct lasers may be combined by an optical multiplexer into a multiplexed transmitted signal that can then be retransmitted from a single multiplexed signal transmitting port.
An optical demultiplexer reverses this process, separating a multiplexed signal that includes a plurality of signals at distinct wavelengths into the corresponding constituent signals. Thus, a multiplexed received signal from a single signal receiving port can be converted by an optical demultiplexer into the separate received signals at respective individual wavelengths that are included in the original multiplexed received signal. In an optical system, therefore, an optical demultiplexer is the interconnecting link between a single optical fiber on which a multiplexed received signal is being communicated and a plurality of optical fibers that each bears an individual of the received signals that had been included in that original multiplexed received signal